Alternatively, you can stop asking, because Nemesis requires all of them to be caught (a de facto technicality, for all of those who are non-FFX fanatic challenged). There's a very nice Bestiary on the Frontsite, not that you noticed, because if you had, you wouldn't be wasting your time here. You also need ten of each Fiend.

Start at Besaid, and retrace your Pilgrimage steps, and you should be fine, if you like systematics, which I'm most certainly sure you do not. But no one cares.